Ross William Ulbricht, 29, accused of running the Silk Road as ‘Dread Pirate Roberts’, is shown in this courtroom sketch in US federal court in San Francisco on 4 October 2013.
Photograph: Stringer/Reuters

Murder-for-hire allegations are central to a New York trial starting this week for a San Francisco man charged with running an online black market where drugs were sold as easily as books and electronics.

US district judge Katherine Forrest overruled defence objections in recent weeks as she concluded prosecutors could introduce evidence about six murder plots into the trial of Ross William Ulbricht. Prospective jurors have filled out questionnaires and formal jury selection starts on Tuesday, when potential jurors will be questioned orally.

Prosecutors say Ulbricht ran an underground website known as Silk Road, where hundreds of kilograms of cocaine, heroin and other drugs were sold to more than 100,000 customers. Ulbricht has pleaded not guilty and is disputing that he operated online under a “Dread Pirate Roberts” alias, an apparent reference to a swashbuckling character in the 1987 comedy The Princess Bride.

The notice on the Silk Road following the FBI’s seizure of its servers. Photograph: David Colbran/ David Colbran/Demotix/Corbis

The government maintains that Ulbricht attempted to protect his operation by asking others to kill those who posed a threat to his business.

“To be sure, the evidence is prejudicial to Ulbricht, and it does inject an element of violence into the case,” Forrest wrote in an opinion letting the evidence be shown to jurors. “However, the prejudicial effect is reduced by the government’s stipulation that no actual murders were carried out.”

She added: “The charges in this case are extremely serious: Ulbricht is charged not with participating in a run-of-the-mill drug distribution conspiracy, but with designing and operating an online criminal enterprise of enormous scope, worldwide reach, and capacity to generate tens of millions of dollars in commissions. Evidence that defendant sought to protect this sprawling enterprise by soliciting murders-for-hire is, in this overall context, not unduly prejudicial.”

Ulbricht was arrested on 1 October 2013 at a San Francisco public library, where FBI agents seized his computer.

The government says he started Silk Road in early 2011, saying he wanted to “create a website where people could buy anything anonymously, with no trail whatsoever that could lead back to them”. It said a spreadsheet found on his computer listed “sr inc” as an asset worth $104m.

Ulbricht was charged in Manhattan with conspiring to commit narcotics trafficking, conspiring to commit computer hacking and conspiring to commit money laundering for a scheme that the government said stretched from January 2011 to September 2013. He is also charged in federal court in Baltimore.